The present invention relates to a surgical method, a surgical tool and artificial implants for repairing knee joints. More particularly, the present invention relates to (i) a surgical method and tool for reshaping a natural patella of the knee joint and fixing a patella implant to the remaining portion of the natural patella, (ii) an artificial tibial knee component implant, (iii) an artificial femoral knee component implant, and (iv) a patella implant.
Joint replacement is becoming increasingly widespread. One of the most widely practiced joint replacement involves the knee joint. In many cases, the replacement of the knee joint with a prosthesis or artificial implant also involves the replacement of a portion of the patella with a prosthetic.
Partial replacement of the patella is widely used in the surgical replacement of a damaged portion of the knee joint. However, it is known that, in a significant percentage of the cases, the patella implant typically fails after five to fifteen years.
One of the typically occurring failures is near or at the periphery of the circular or elliptical patella implant, where the thickness of the patella implant material, typically high molecular weight high density polyethylene (HDPE), is at its smallest.
A failing patella could lead to significant pain in the patient and typically requires a second operation to replace the failed patella implant and often the entire prosthetic joint.
U.S. Pat. No. 5,580,353 discloses a prosthetic patella implant adapted to substantially structurally fit a remaining portion of the natural patella with maximal preserving of healthy natural tissue and minimal wear of the implant.
U.S. patent application Ser. No. 08/735,927 now U.S. Pat. No. 5,824,099 discloses a surgical method and tool for preparing a natural patella by removing a portion thereof to accept the patella implant described in U.S. Pat. No. 5,580,353.
In one aspect, like U.S. Pat. No. 5,580,353 and U.S. patent application Ser. No. 08/735,927, now U.S. Pat. No. 5,824,099 the present invention concerns a prosthetic patella implant adapted to substantially structurally fit a remaining portion of the natural patella with maximal preserving of healthy natural tissue and minimal wear of the implant and a surgical method and tool for preparing a natural patella by removing a portion thereof to accept the patella implant.
U.S. Pat. Nos. 4,550,448; 4,653,488; 4,298,992; 4,834,756; 4,944,756; 5,035,700 and 5,192,324, which are incorporated by reference as if fully set forth herein, disclose artificial tibial knee component implants to be used, for example, as the tibial knee component in total knee joint implants.
These implants are provided with cylindrical, rectangular or T shaped in cross section stems implantable into a cut formed into a tibia bone.
As such, these implants suffer disadvantages in engaging and in harmonically functioning with the reshaped tibial bone as further detailed below.
Thus, in another aspect, the present invention concerns improvements to the tibial knee component implant stem.
U.S. Pat. Nos. 4,298,992, 4,950,298; 5,047,058; 5,053,037; 5,100,408; 5,282,803; 5,514,140; 5,354,075; 5,417,694 and 5,549,688; UK Pat. No. 2067412 and AU Pat. No. 542787, which are incorporated by reference as if fully set forth herein, disclose artificial femoral knee component implants to be used, for example, as the femoral knee component in total knee joint implants.
These implants are provided with a substantially linear groove which is expected to simulate the trochlear groove of a natural femur bone and which is expected to serve, when implanted, as a guiding route for the patella (or patella implant) with respect to the femoral implant.
Featuring a linear groove, these femoral implants suffer disadvantages in simulating the natural relative knee components movement, wherein in the natural case the patella follows helicoid (sinuous) course with respect to the femur bone.
Therefore, in another aspect, the present invention concerns improvements to the shape of a femoral knee component implant, so as to allow for better simulation of the natural knee movement.